A California dairy cow recently tested positive[2] for bovine spongiform encephalopathy (BSE), more commonly known as mad cow disease. While the news has resurrected fears about the illness, the United States Department of Agriculture has been quick to highlight that the cow, located in California’s Central Valley, was not tied to the food chain, and that humans are not at risk of contracting the human form, variant Creutzfeldt-Jakob disease, which causes rapid brain degeneration. This assurance has not prevented some South Korean retailers from halting sales of US beef into the country as memories of the massive UK outbreak in the early 1990s which claimed the lives of 180,000 cattle and over 150 people remain fresh in the consciousness of many.

The is the fourth instance of Mad Cow Disease to have been discovered in US history. It was long believed that cattle were infected with BSE by eating feed [5]that included spine and brain tissue of other cows[6] who had consumed the meat of sheep infected with scrapie[7]. But some scientists have since hypothesized that the disease may develop spontaneously in cattle. Federal officials believe that the recent instance in California[8] was a indeed caused by an atypical genetic malformation, as CBS reported[2]. “It was just a random mutation that can happen every once in a great while in an animal,” Bruce Akey, director of the New York State Veterinary Diagnostic Laboratory at Cornell University, told the AP. “Random mutations go on in nature all the time.” Federal officials further emphasized that the infected cow had not eaten contaminated feed.

The AP[9] described the discovery of the illness as a “stroke of luck,” since only 40,000, or 0.1 percent of cattle are tested each year for the BSE, but in light of the discovery, officials do plan to take additional precautions. “State and federal agriculture officials plan to test other cows that lived in the same feeding herd as the infected bovine,” said Michael Marsh, chief executive of Western United Dairymen, who was briefed on the plan. “They also plan to test cows born at around the same time the diseased cow was.”

As South Korean retailers exhibit caution, the Washington Post reports that[10] “South Korea said it will strengthen quarantine inspections of U.S. beef after the case.” Other countries which import US beef[11], including the UK, Canada and Japan have not announced any changes to their import of US beef, as many await confirmation of additional tests to be conducted by the United Nations’ Food and Agriculture Organization and the World Organisation for Animal Health.